Humans have produced and consumed ethanol for industrial, recreational, and medical purposes for millennia, with a broad spectrum of effects on human health. Considerable evidence implicates ligand-gated ion channels as molecular targets of ethanol. Precise structural characterization of the interaction of alcohol with these channels would aid the elucidation of genetic variation in alcohol sensitivity, and facilitate the development of pharmaceutical agents to treat alcohol disorders. However, technical challenges to the purification and crystallization of membrane proteins have impeded the structure determination of an ion channel bound to ethanol. The recent publication of the structure of GLIC, a prokaryotic homolog of ligand-gated ion channels in the cys-loop receptor family, poses a novel opportunity to characterize alcohol modulation of an ion channel in structural detail. This proposal aims to explore alcohol modulation of GLIC, identify specific GLIC sites associated with alcohol binding, and generate GLIC mutants with enhanced alcohol modulation. The realization of these goals will establish GLIC as a structurally accessible model system for alcohol modulation, and reveal critical details of alcohol binding to ligand-gated ion channels. PUBLIC HEALTH RELEVANCE: Despite the longstanding historical role of alcohol (ethanol) consumption in human society, we know remarkably little about how alcohol affects the brain. By characterizing the binding of alcohol to brain targets in detail, these experiments will help to explain why some individuals are more sensitive to alcohol use and dependence than others, and in the long run may aid the development of new approaches to combat alcohol- related disorders.